Add `hide-input` cell tags

This can now be done via this VS Code extension: https://marketplace.visualstudio.com/items?itemName=ms-toolsai.vscode-jupyter-cell-tags

Doing it automatically (#717) remains ideal IMO, but this will make the documentation more approachable in the meantime.

Start by reviewing the VS Code Jupyter Cell Tags extension linked in the issue and locating the repository's documentation notebooks or examples. Add the `hide-input` tags where they improve approachability, then verify that the affected notebooks render with inputs hidden as intended.

Written by the indexing model from the issue text.